This application claims the priority of Japanese Patent Applications No. 2001-102275 filed on Mar. 30, 2001 which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a configuration of an electronic endoscope apparatus in which electronic endoscopes having image pickup elements with different number of pixels mounted thereon can be connected to a processor device.
2. Description of the Related Art
In an electronic endoscope apparatus, an electronic endoscope having a CCD (Charge Coupled Device) as an image pickup element at its top end is connected to a processor. A video signal acquired by the CCD undergoes a predetermined video processing in the electronic endoscope and the processor, whereby a video of the observed subject is displayed on a monitor.
In recent years, the electronic endoscopes mounting a CCD with a greater number of pixels have been manufactured in a relatively short cycle one after another to produce a high resolution video, whereby the electronic endoscopes having the CCD with a different number of pixels are connected to the same processor. For example, a CCD 1 having 410 thousand pixels, a CCD 2 having 270 thousand pixels, and a CCD 3 having 190 thousand pixels are provided, as shown in FIGS. 8A to 8C.
The CCD 1 having 410 thousand pixels as shown in FIG. 8A has an image pickup area consisting of 768 pixels in a horizontal direction and 494 lines in a vertical direction. The CCD 2 having 270 thousand pixels as shown in FIG. 8B has an image pickup area consisting of 510 pixels in the horizontal direction and 492 lines in the vertical direction. And the CCD 3 having 190 thousand pixels as shown in FIG. 8C has an image pickup area consisting of 362 pixels in the horizontal direction and 492 lines in the vertical direction.
However, with this conventional electronic endoscope apparatus, since electronic endoscopes having CCDs with different numbers of pixels mounted thereon can be connected to the same processor device, different frequencies (which are required to drive the CCDs and process signals) is generated correspondingly to the number of pixels, thereby requiring complicated circuits and signal processing.
That is, as a drive frequency required to read out pixel information, 14.32 MHz is used for the 410 thousand pixels in FIG. 8(A), 9.58 MHz is used for the 270 thousand pixels in FIG. 8(B), and 6.75 MHz is used for the 190 thousand pixels in FIG. 8(C). Accordingly, these drive frequencies and other signal processing frequencies must be formed correspondingly to the numbers of CCD pixels in the electronic endoscope, thus requiring complicated circuits for generating these frequencies as well as complicated video processing based on these frequencies.